In the US it has already killed four million pigs in the past year alone.

It’s no threat to humans but kills almost every piglet infected, sparking fears of bacon shortages and high prices. Penny Johnston, of the National Farmers’ Union warned: “The virus would have a very high impact and the potential to spread quickly.

“Pig farms have already been going through a hard time and can’t afford to be hit with this. It could be devastating.

“Any big disease impacts on business and availability of products, so prices go up if it happens”

Penny Johnston, of the National Farmers’ Union

“Any big disease impacts on business and availability of products, so prices go up if it happens.

“That’s not a good thing for the industry because if the market has to go to other countries for products, it’s hard to win them back.”

The virus has so far spread from China to America and then on to Canada and Mexico.

Experts believe a special ingredient called SDPP – found in feed given to piglets – could be the cause.

It has been banned from the UK, although other pig feeds which use small quantities of it could still slip into the country.

However, farmers have also been warned the disease could be transmitted by equipment or people arriving on their smallholding from outside.

And National Pig Assoc-iation chairman Richard Longthorp added: “If it did enter the UK, I think it would spread far more quickly and extensively than in America.”